Both Union and Confederate leaders invoked God to advance their causes during the Civil War. But Abraham Lincoln refused to claim the divine on his side. Heather Curtis, a professor of religion at Tufts University, explains Lincoln’s approach to faith, and why he didn’t join a church. She also delves into the religious roots of William McKinley’s assertive foreign policy, and Woodrow Wilson’s leadership during World War I and his founding of the League of Nations.